1. Field of the Invention
The present invention relates to a system for working deposits of fluids, which in particular, but not exclusively, is applicable to offshore deposits of hydrocarbons, with the system being adapted primarily to increase the recovery of the fluids, especially when the fluids are under low pressure in the deposits, or are difficult to extract, and to simplify the installations and their utilization, while improving their safety in operation.
2. Discussion of the Prior Art
Generally, it is widely known that the working of offshore deposits of hydrocarbons requires the emplacement of a system which is constituted, as on land, primarily of wells equipped with subsea and/or raised production heads, connections between the production heads and production installations, wherein the connections can be very short if the production heads are close to the production installations, with the production installations themselves rendering it possible to separate and process the various phases of the effluent, and means for conveying the products extracted from the deposit to a storage location. All or portions of the arrangements described hereinabove are usually concentrated within one or more structures fixed to the seabed or are assembled on the decks of floating structures.
Depending upon the rate of flow, the nature of the effluent and the exterior environmental conditions, the mounting of the installations may necessitate the provision of supporting and protective structures reaching the limits of present-day technological capabilities. Finally, when the waters are of great depths and/or the encountered environmental conditions are extremely severe in nature, the adaptation of conventional working systems to these conditions becomes problematic, and generally extremely expensive.
Furthermore, the control of flows and pressures of the effluent, as well as those of the components employed to maintain them below a predetermined upper limit, in view of the high level of safety which is required in these confined installations, combine to render these systems highly complex, also requiring a relatively large number of skilled personnel to operate and supervise the systems.
Moreover, as on land, the recovery of the fluids in situ in the deposit will often be limited by an abandonment pressure which is a function of the depth of the deposit and the devices which may be utilized to assist with production until it reaches the installations for the separation and processing of the effluent.
Furthermore, in the case of fluids which are difficult to extract because of their physical characteristics and the conditions of the deposit, it becomes apparent that the movement of these fluids upwardly through the intervening water to the surface installations will tend to make the encountered problems more difficult to solve and, finally, will limit the flow from the wells and the recovery of the fluids from the deposit as a result of energy losses and reduction in the temperature of the flowing effluent, and thus raise the abandonment pressure for the deposit.
Finally, if the wells are equipped with subsea production heads, the maintenance of the wells, which is necessary during the life of a deposit, will be feasible cost.